This study will test hypotheses concerning factors important in the development of amblyopia following paralytic strabismus. The visual abilities of animals with paralysis of the extraocular muscles produced as neonates or as adults will be evaluated neuro-ophthalmologically and by behavioral tests of visual acuity, brightness discrimination and movement discrimination. These experiments are designed to determine whether unbalanced visual input from the two eyes or a fundamental defect in ocular motility is a critical factor in producing amblyopia.